The present invention relates in general to an automotive cooling system and pertains, more particularly, to a cooling system for a motor vehicle that is essentially a non-pressure system that is thus adapted to operate at ambient pressure.
Automotive cooling systems are adapted to operate under a certain degree of pressure so as to raise the boiling point of the coolant beyond its boiling point at standard temperature and pressure. Thus, to improve the cooling efficiency, automobiles use a pressure cap on the radiator such as illustrated herein in the prior art drawing of FIG. 1. FIG. 1 schematically illustrates the radiator 10 with the standard gooseneck 12 and supporting the pressure cap 14. It is noted that the gooseneck 12 is provided with an outlet port at 16 to which is connected the line 18 that essentially connects from the radiator to the expansion tank 20. The expansion tank 20 is provided also with a cap 22 and a vent line 24.
It is noted in the prior art diagram of FIG. 1 that the cap 14 is a pressure cap that seals at the top of the gooseneck at 15 and furthermore provides a pressurizing seal at 17.
At sea level, where atmospheric pressure is about 15 p.s.i., water boils at 212.degree. F. At higher altitudes, where atmospheric pressure is less, water boils at lower temperatures. Higher pressures increase the temperature required to boil water. The use of a pressure cap on the radiator increases the air pressure within the cooling system several pounds per square inch. Thus, the water may be circulated at higher temperatures without boiling.
The pressure cap 14 contains two valves, a blow-off valve and a vacuum valve. The blow-off valve consists of a valve held against a valve seat by a calibrated spring. In FIG. 1 note the spring 19. The spring holds the valve closed providing the seal at 17 so that pressure is produced in the cooling system. Pressure rises above that for which the system is designed, the blow-off valve is raised off its seat, relieving the excessive pressure. Pressure caps are designed to provide as much as 18 pounds of pressure per square inch in the cooling system; this increasing the boiling point of the water to almost 250.degree. F. This prior pressurized system is completely filled with a coolant as illustrated in FIG. 1 and is sealed with a tight cap that has a spring loaded release and that also includes a vacuum valve. As the engine starts to warm up, pressure starts to build in the system. When it reaches the amount of pressure the cap is designed for, such as the aforementioned 18 pounds, coolant is released, which passes through the hose 18 into the recovery or expansion tank 20. The hose enters the tank at the bottom as illustrated in FIG. 1 so that the end is always in the coolant. This insures exclusion of air into the system during the time of cool-down, when the engine is turned off, and when the system reverts from pressure to vacuum. It is at this time that the vacuum valve in the radiator cap comes into use, opening and using the vacuum in the cooling system to draw the coolant from the recovery tank back into the radiator. Thus, the system is kept full of coolant at all times. One of the problems, however, is that when a leak occurs, the excessive pressure accelerates the leak and vacuum will introduce unwanted air into the system.
Because of these excess pressures in present day cooling systems, there are scores of places in the cooling system where components thereof are subject to internal pressures. For example, radiator fluid tubes can corrode or be weakened by mechanical flexing, leaving a poor supporting material to contain the coolant. The same is true for the heater core. With these pressurized systems, the heater core and main radiator hoses eventually weaken from the destructive effects of the substantially increased pressures. Because of these pressurized systems, there is a need for constant retightening of hose clamps, but this can create tears in other weakened points where coolant can escape. Then there are the engine freeze plugs, which, if sufficiently corroded, can be blown out by excess pressure. Water pump shaft seals, O-rings, and block mounting gaskets are also potential weak points in these highly pressurized systems. In some vehicles, water jacket channels run between major engine components, such as the intake manifold and the block; the gasketed joints can also thus be vulnerable to pressure induced leakage. Once a serious pressure leak has occurred, the motorist runs a great risk of catastrophic damage to the engine. The engine block and the crank case oil can absorb heat for a short period of time, but soon thereafter, the engine seizes and is essentially destroyed.
Accordingly, it is an object of the present invention to provide an approved automotive engine cooling system which is essentially a non-pressure system and one in which provision is made for an expansion tank used in association with the cooling system.
Another object of the present invention is to provide a non-pressure cooling system for an automobile in which the coolant expansion tank is connected in a feedback arrangement with the automotive cooling system so as to maintain the proper amount of coolant in the system at all times, but without the attendant problems associated with present high pressure systems.